DESCRIPTION: (from abstract). Chronic blepharitis, one of the most common conditions seen in the ophthalmologist's office, is difficult to treat effectively. It is an extremely complex condition that manifests several different and overlapping arrays of signs and symptoms (crusting of lid margin, itching and burning eyelids, lid inflammation, swelling, conjunctival inflammation, localized corneal damage). Evidence indicates that meibomian gland abnormalities are involved in several forms of this disease, principally through their lipid secretions. The basic premise is that biochemical changes of meibomian gland lipids cause many signs directly, while lipid composition itself predisposes secretions to other changes resulting from microbial activity or other factors. Using analytical techniques that allow us to analyze the meibomian secretions from individual patients, understand how chronic blepharitis disease signs are caused by changes in lipid composition, ascertain why the lipid modifications occur, develop new treatments which will reverse or mask the deleterious lipid modifications, define further the structural and physiological characteristics of the tear lipid layer, and define the role lipids (especially the polar lipid phase) play in keratoconjunctivitis. Aim I tests specific hypotheses about the relations between lipid abnormalities in chronic blepharitis and specific mechanisms of action. Aim 2 tests the hypothesis that the relative level of lipid unsaturation, cholesterol and polyol (e.g. sugar, cerebroside) content directly affects meiburn fluidity. Aim 3 tests the hypothesis that infant meibum differs from adult in fatty acid and alcohol type or in polar lipids. Aim 4 tests predictions from the hypothesis that the biophysical characteristics of meibum in the tear film are a direct result of the meibum chemical (lipid) composition. Methods include non-destructive HPLC as well as GC-MS to analyze patient meibum, and standard lipid mixtures based on the composition of patient meibum for physical measurements.